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* Add support for bitreverse primopAlexandre2019-04-019-5/+50
| | | | | | This commit includes the necessary changes in code and documentation to support a primop that reverses a word's bits. It also includes a test.
* Visibility: handle multiple units with the same nameMichael Peyton Jones2019-03-291-13/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fixes #16228. The included test case is adapted from the reproduction in the issue, and fails without this patch. ------ We compute an initial visilibity mapping for units based on what is present in the package databases. To seed this, we compute a set of all the package configs to add visibilities for. However, this set was keyed off the unit's *package name*. This is correct, since we compare packages across databases by version. However, we would only ever consider a single, most-preferable unit from the database in which it was found. The effect of this was that only one of the libraries in a Cabal package would be added to this initial set. This would cause attempts to use modules from the omitted libraries to fail, claiming that the package was hidden (even though `ghc-pkg` would correctly show it as visible). A solution is to do the selection of the most preferable packages separately, and then be sure to consider exposing all units in the same package in the same package db. We can do this by picking a most-preferable unit for each package name, and then considering exposing all units that are equi-preferable with that unit. ------ Why wasn't this bug apparent to all people trying to use sub-libraries in Cabal? The answer is that Cabal explicitly passes `-package` and `-package-id` flags for all the packages it wants to use, rather than relying on the state of the package database. So this bug only really affects people who are trying to use package databases produced by Cabal outside of Cabal itself. One particular example of this is the way that the Nixpkgs Haskell infrastructure provides wrapped GHCs: typically these are equipped with a package database containing all the needed package dependencies, and the user is not expected to pass `-package` flags explicitly.
* Fix a few broken Trac links [skip ci]Chaitanya Koparkar2019-03-271-1/+1
| | | | This patch only attempts to fix links that don't automatically re-direct to the correct URL.
* Minor refactoring in copy array primops:Ömer Sinan Ağacan2019-03-271-15/+17
| | | | | | | | | | - `emitCopySmallArray` now checks size before generating code and doesn't generate any code when size is 0. `emitCopyArray` already does this so this makes small/large array cases the same in argument checking. - In both `emitCopySmallArray` and `emitCopyArray` read the `dflags` after checking the argument.
* Update Wiki URLs to point to GitLabTakenobu Tani2019-03-2545-61/+61
| | | | | | | | | | | | | | | | | | | | | | | This moves all URL references to Trac Wiki to their corresponding GitLab counterparts. This substitution is classified as follows: 1. Automated substitution using sed with Ben's mapping rule [1] Old: ghc.haskell.org/trac/ghc/wiki/XxxYyy... New: gitlab.haskell.org/ghc/ghc/wikis/xxx-yyy... 2. Manual substitution for URLs containing `#` index Old: ghc.haskell.org/trac/ghc/wiki/XxxYyy...#Zzz New: gitlab.haskell.org/ghc/ghc/wikis/xxx-yyy...#zzz 3. Manual substitution for strings starting with `Commentary` Old: Commentary/XxxYyy... New: commentary/xxx-yyy... See also !539 [1]: https://gitlab.haskell.org/bgamari/gitlab-migration/blob/master/wiki-mapping.json
* base: Remove `Monad(fail)` method and reexport `MonadFail(fail)` insteadHerbert Valerio Riedel2019-03-227-117/+26
| | | | | | As per https://prime.haskell.org/wiki/Libraries/Proposals/MonadFail Coauthored-by: Ben Gamari <ben@well-typed.com>
* Remove unused XArrApp and XArrForm extension pointsRyan Scott2019-03-202-9/+0
| | | | | | !301 removed the `HsArrApp` and `HsArrForm` constructors, which renders the corresponding extension points `XArrApp` and `XArrForm` useless. This patch finally rips them out.
* Check.hs: Fix a few typosSimon Jakobi2019-03-201-5/+5
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* Reject nested predicates in impredicativity checkingRyan Scott2019-03-202-41/+45
| | | | | | | | | | | | | | | | | | | | | | | | | When GHC attempts to unify a metavariable with a type containing foralls, it will be rejected as an occurrence of impredicativity. GHC was /not/ extending the same treatment to predicate types, such as in the following (erroneous) example from #11514: ```haskell foo :: forall a. (Show a => a -> a) -> () foo = undefined ``` This will attempt to instantiate `undefined` at `(Show a => a -> a) -> ()`, which is impredicative. This patch catches impredicativity arising from predicates in this fashion. Since GHC is pickier about impredicative instantiations, some test cases needed to be updated to be updated so as not to fall afoul of the new validity check. (There were a surprising number of impredicative uses of `undefined`!) Moreover, the `T14828` test case now has slightly less informative types shown with `:print`. This is due to a a much deeper issue with the GHCi debugger (see #14828). Fixes #11514.
* Remove deprecated reinitializeGlobalsKrzysztof Gogolewski2019-03-191-7/+0
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* Simplify monadic codeKrzysztof Gogolewski2019-03-192-13/+10
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* Fix typosKrzysztof Gogolewski2019-03-196-7/+7
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* Replace nOfThem by replicateKrzysztof Gogolewski2019-03-196-15/+12
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* ghc-heap: Introduce closureSizeBen Gamari2019-03-171-0/+7
| | | | | | This function allows the user to compute the (non-transitive) size of a heap object in words. The "closure" in the name is admittedly confusing but we are stuck with this nomenclature at this point.
* compiler: Disable atomic renaming on WindowsBen Gamari2019-03-161-1/+13
| | | | | As discussed in #16450, this feature regresses CI on Windows, causing non-deterministic failures due to missing files.
* Add location to the extra-constraints wildcardSimon Peyton Jones2019-03-161-3/+4
| | | | | | | The extra-constraints wildcard had lost its location (issue #16431). Happily this is easy to fix. Lots of error improvements.
* Improve error recovery in the typecheckerSimon Peyton Jones2019-03-168-178/+264
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Issue #16418 showed that we were carrying on too eagerly after a bogus type signature was identified (a bad telescope in fact), leading to a subsequent crash. This led me in to a maze of twisty little passages in the typechecker's error recovery, and I ended up doing some refactoring in TcRnMonad. Some specfifics * TcRnMonad.try_m is now called attemptM. * I switched the order of the result pair in tryTc, to make it consistent with other similar functions. * The actual exception used in the Tc monad is irrelevant so, to avoid polluting type signatures, I made tcTryM, a simple wrapper around tryM, and used it. The more important changes are in * TcSimplify.captureTopConstraints, where we should have been calling simplifyTop rather than reportUnsolved, so that levity defaulting takes place properly. * TcUnify.emitResidualTvConstraint, where we need to set the correct status for a new implication constraint. (Previously we ended up with an Insoluble constraint wrapped in an Unsolved implication, which meant that insolubleWC gave the wrong answer.
* PPC NCG: Use liveness information in CmmCallPeter Trommler2019-03-154-42/+49
| | | | | | | | | | | | | | | | | We make liveness information for global registers available on `JMP` and `BCTR`, which were the last instructions missing. With complete liveness information we do not need to reserve global registers in `freeReg` anymore. Moreover we assign R9 and R10 to callee saves registers. Cleanup by removing `Reg_Su`, which was unused, from `freeReg` and removing unused register definitions. The calculation of the number of floating point registers is too conservative. Just follow X86 and specify the constants directly. Overall on PowerPC this results in 0.3 % smaller code size in nofib while runtime is slightly better in some tests.
* Report better suggestion for GADT data constructorSimon Peyton Jones2019-03-151-13/+9
| | | | This addresses issue #16427. An easy fix.
* Update Trac ticket URLs to point to GitLabRyan Scott2019-03-15166-850/+850
| | | | | This moves all URL references to Trac tickets to their corresponding GitLab counterparts.
* Remove the GHCi debugger's panicking isUnliftedType checkRyan Scott2019-03-151-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The GHCi debugger has never been that robust in the face of higher-rank types, or even types that are _interally_ higher-rank, such as the types of many class methods (e.g., `fmap`). In GHC 8.2, however, things became even worse, as the debugger would start to _panic_ when a user tries passing the name of a higher-rank thing to `:print`. This all ties back to a strange `isUnliftedType` check in `Debugger` that was mysteriously added 11 years ago (in commit 4d71f5ee6dbbfedb4a55767e4375f4c0aadf70bb) with no explanation whatsoever. After some experimentation, no one is quite sure what this `isUnliftedType` check is actually accomplishing. The test suite still passes if it's removed, and I am unable to observe any differences in debugger before even with data types that _do_ have fields of unlifted types (e.g., `data T = MkT Int#`). Given that this is actively causing problems (see #14828), the prudent thing to do seems to be just removing this `isUnliftedType` check, and waiting to see if anyone shouts about it. This patch accomplishes just that. Note that this patch fix the underlying issues behind #14828, as the debugger will still print unhelpful info if you try this: ``` λ> f :: (forall a. a -> a) -> b -> b; f g x = g x λ> :print f f = (_t1::t1) ``` But fixing this will require much more work, so let's start with the simple stuff for now.
* Fix #16411 by making dataConCannotMatch aware of (~~)Ryan Scott2019-03-131-4/+7
| | | | | | | | The `dataConCannotMatch` function (which powers the `-Wpartial-fields` warning, among other things) had special reasoning for explicit equality constraints of the form `a ~ b`, but it did not extend that reasoning to `a ~~ b` constraints, leading to #16411. Easily fixed.
* Remove duplicate functions in StgCmmUtils, use functions from CgUtilsÖmer Sinan Ağacan2019-03-122-51/+11
| | | | Also remove unused arg from get_Regtable_addr_from_offset
* Use transSuperClasses in TcErrorsSimon Peyton Jones2019-03-122-12/+31
| | | | | | | | | | Code in TcErrors was recursively using immSuperClasses, which loops in the presence of UndecidableSuperClasses. Better to use transSuperClasses instead, which has a loop-breaker mechanism built in. Fixes issue #16414.
* Change the warning in substTy back to an assertionKrzysztof Gogolewski2019-03-114-6/+5
| | | | | | | We'd like to enforce the substitution invariant (Trac #11371). In a492af06d326453 the assertion was downgraded to a warning; I'm restoring the assertion and making the calls that don't maintain the invariant as unchecked.
* NCG: correctly escape path strings on Windows (#16389)Sylvain Henry2019-03-093-3/+15
| | | | | GHC native code generator generates .incbin and .file directives. We need to escape those strings correctly on Windows (see #16389).
* compiler: Refactor: extract `withAtomicRename`Niklas Hambüchen2019-03-092-8/+29
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* compiler: Write .o files atomically. See #14533Niklas Hambüchen2019-03-091-1/+6
| | | | | | | | | | | | | | | | | | | This issue was reproduced with, and the fix confirmed with, the `hatrace` tool for syscall-based fault injection: https://github.com/nh2/hatrace The concrete test case for GHC is at https://github.com/nh2/hatrace/blob/e23d35a2d2c79e8bf49e9e2266b3ff7094267f29/test/HatraceSpec.hs#L185 A previous, nondeterministic reproducer for the issue was provided by Alexey Kuleshevich in https://github.com/lehins/exec-kill-loop Signed-off-by: Niklas Hambüchen <niklas@fpcomplete.com> Reviewed-by: Alexey Kuleshevich <alexey@fpcomplete.com>
* Stop inferring over-polymorphic kindsSimon Peyton Jones2019-03-097-109/+80
| | | | | | | | | | | | | | | | | | | | | | | | | | | Before this patch GHC was trying to be too clever (Trac #16344); it succeeded in kind-checking this polymorphic-recursive declaration data T ka (a::ka) b = MkT (T Type Int Bool) (T (Type -> Type) Maybe Bool) As Note [No polymorphic recursion] discusses, the "solution" was horribly fragile. So this patch deletes the key lines in TcHsType, and a wodge of supporting stuff in the renamer. There were two regressions, both the same: a closed type family decl like this (T12785b) does not have a CUSK: type family Payload (n :: Peano) (s :: HTree n x) where Payload Z (Point a) = a Payload (S n) (a `Branch` stru) = a To kind-check the equations we need a dependent kind for Payload, and we don't get that any more. Solution: make it a CUSK by giving the result kind -- probably a good thing anyway. The other case (T12442) was very similar: a close type family declaration without a CUSK.
* Fix #13839: GHCi warnings do not respect the default module headerwip/magic-carpet-rideRoland Senn2019-03-081-4/+34
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* TH: support raw bytes literals (#14741)Sylvain Henry2019-03-082-0/+22
| | | | | | | | | | | | | | | | | | | GHC represents String literals as ByteString internally for efficiency reasons. However, until now it wasn't possible to efficiently create large string literals with TH (e.g. to embed a file in a binary, cf #14741): TH code had to unpack the bytes into a [Word8] that GHC then had to re-pack into a ByteString. This patch adds the possibility to efficiently create a "string" literal from raw bytes. We get the following compile times for different sizes of TH created literals: || Size || Before || After || Gain || || 30K || 2.307s || 2.299 || 0% || || 3M || 3.073s || 2.400s || 21% || || 30M || 8.517s || 3.390s || 60% || Ticket #14741 can be fixed if the original code uses this new TH feature.
* Use captureTopConstraints in TcRnDriver callsSimon Peyton Jones2019-03-083-10/+28
| | | | | | | | | | | | | | | | | Trac #16376 showed the danger of failing to report an error that exists only in the unsolved constraints, if an exception is raised (via failM). Well, the commit 5c1f268e (Fail fast in solveLocalEqualities) did just that -- i.e. it found errors in the constraints, and called failM to avoid a misleading cascade. So we need to be sure to call captureTopConstraints to report those insolubles. This was wrong in TcRnDriver.tcRnExpr and in TcRnDriver.tcRnType. As a result the error messages from test T13466 improved slightly, a happy outcome.
* Always do the worker/wrapper split for NOINLINEsSebastian Graf2019-03-072-7/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | Trac #10069 revealed that small NOINLINE functions didn't get split into worker and wrapper. This was due to `certainlyWillInline` saying that any unfoldings with a guidance of `UnfWhen` inline unconditionally. That isn't the case for NOINLINE functions, so we catch this case earlier now. Nofib results: -------------------------------------------------------------------------------- Program Allocs Instrs -------------------------------------------------------------------------------- fannkuch-redux -0.3% 0.0% gg +0.0% +0.1% maillist -0.2% -0.2% minimax 0.0% -0.8% -------------------------------------------------------------------------------- Min -0.3% -0.8% Max +0.0% +0.1% Geometric Mean -0.0% -0.0% Fixes #10069. ------------------------- Metric Increase: T9233 -------------------------
* Fix #16391 by using occCheckExpand in TcValidityRyan Scott2019-03-074-26/+88
| | | | | | | | | | | | | The type-variables-escaping-their-scope-via-kinds check in `TcValidity` was failing to properly expand type synonyms, which led to #16391. This is easily fixed by using `occCheckExpand` before performing the validity check. Along the way, I refactored this check out into its own function, and sprinkled references to Notes to better explain all of the moving parts. Many thanks to @simonpj for the suggestions. Bumps the haddock submodule.
* Fix #16385 by appending _maybe to a use of lookupGlobalOccRyan Scott2019-03-061-8/+24
| | | | | | | | | `instance forall c. c` claimed that `c` was out of scope because the renamer was invoking `lookupGlobalOcc` on `c` (in `RnNames.getLocalNonValBinders`) without binding `c` first. To avoid this, this patch changes GHC to invoke `lookupGlobalOcc_maybe` on `c` instead, and if that returns `Nothing`, then bail out, resulting in a better error message.
* Rip out object splittingBen Gamari2019-03-0519-325/+62
| | | | | | | | | | | | | | | The splitter is an evil Perl script that processes assembler code. Its job can be done better by the linker's --gc-sections flag. GHC passes this flag to the linker whenever -split-sections is passed on the command line. This is based on @DemiMarie's D2768. Fixes Trac #11315 Fixes Trac #9832 Fixes Trac #8964 Fixes Trac #8685 Fixes Trac #8629
* Fix map/coerce rule for newtypes with wrappersKrzysztof Gogolewski2019-03-053-29/+32
| | | | | | | | This addresses Trac #16208 by marking newtype wrapper unfoldings as compulsory. Furthermore, we can remove the special case for newtypes in exprIsConApp_maybe (introduced in 7833cf407d1f).
* Be more careful when naming TyCon bindersSimon Peyton Jones2019-03-0510-356/+595
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch fixes two rather gnarly test cases: * Trac #16342 (mutual recursion) See Note [Tricky scoping in generaliseTcTyCon] * Trac #16221 (shadowing) See Note [Unification variables need fresh Names] The main changes are: * Substantial reworking of TcTyClsDecls.generaliseTcTyCon This is the big change, and involves the rather tricky function TcHsSyn.zonkRecTyVarBndrs. See Note [Inferring kinds for type declarations] and Note [Tricky scoping in generaliseTcTyCon] for the details. * bindExplicitTKBndrs_Tv and bindImplicitTKBndrs_Tv both now allocate /freshly-named/ unification variables. Indeed, more generally, unification variables are always fresh; see Note [Unification variables need fresh Names] in TcMType * Clarify the role of tcTyConScopedTyVars. See Note [Scoped tyvars in a TcTyCon] in TyCon As usual, this dragged in some more refactoring: * Renamed TcMType.zonkTyCoVarBndr to zonkAndSkolemise * I renamed checkValidTelescope to checkTyConTelescope; it's only used on TyCons, and indeed takes a TyCon as argument. * I folded the slightly-mysterious reportFloatingKvs into checkTyConTelescope. (Previously all its calls immediately followed a call to checkTyConTelescope.) It makes much more sense there. * I inlined some called-once functions to simplify checkValidTyFamEqn. It's less spaghetti-like now. * This patch also fixes Trac #16251. I'm not quite sure why #16251 went wrong in the first place, nor how this patch fixes it, but hey, it's good, and life is short.
* Revert "compiler: Write .o files atomically. See #14533"Ben Gamari2019-03-041-6/+1
| | | | This reverts commit 0e2d300a59b1b5c167d2e7d99a448c8663ba6d7d.
* Revert "compiler: Refactor: extract `withAtomicRename`"Ben Gamari2019-03-042-29/+8
| | | | This reverts commit e8a08f400744a860d1366c6680c8419d30f7cc2a.
* Lexer: turn some fatal errors into non-fatal onesAlec Theriault2019-03-011-18/+24
| | | | | | | | | | The following previously fatal lexer errors are now non-fatal: * errors about enabling `LambdaCase` * errors about enabling `NumericUnderscores` * errors about having valid characters in primitive strings See #16270
* Visible dependent quantificationRyan Scott2019-03-0122-136/+405
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This implements GHC proposal 35 (https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0035-forall-arrow.rst) by adding the ability to write kinds with visible dependent quantification (VDQ). Most of the work for supporting VDQ was actually done _before_ this patch. That is, GHC has been able to reason about kinds with VDQ for some time, but it lacked the ability to let programmers directly write these kinds in the source syntax. This patch is primarly about exposing this ability, by: * Changing `HsForAllTy` to add an additional field of type `ForallVisFlag` to distinguish between invisible `forall`s (i.e, with dots) and visible `forall`s (i.e., with arrows) * Changing `Parser.y` accordingly The rest of the patch mostly concerns adding validity checking to ensure that VDQ is never used in the type of a term (as permitting this would require full-spectrum dependent types). This is accomplished by: * Adding a `vdqAllowed` predicate to `TcValidity`. * Introducing `splitLHsSigmaTyInvis`, a variant of `splitLHsSigmaTy` that only splits invisible `forall`s. This function is used in certain places (e.g., in instance declarations) to ensure that GHC doesn't try to split visible `forall`s (e.g., if it tried splitting `instance forall a -> Show (Blah a)`, then GHC would mistakenly allow that declaration!) This also updates Template Haskell by introducing a new `ForallVisT` constructor to `Type`. Fixes #16326. Also fixes #15658 by documenting this feature in the users' guide.
* Treat kind/type variables identically, demolish FKTVVladislav Zavialov2019-02-278-481/+206
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implements GHC Proposal #24: .../ghc-proposals/blob/master/proposals/0024-no-kind-vars.rst Fixes Trac #16334, Trac #16315 With this patch, scoping rules for type and kind variables have been unified: kind variables no longer receieve special treatment. This simplifies both the language and the implementation. User-facing changes ------------------- * Kind variables are no longer implicitly quantified when an explicit forall is used: p :: Proxy (a :: k) -- still accepted p :: forall k a. Proxy (a :: k) -- still accepted p :: forall a. Proxy (a :: k) -- no longer accepted In other words, now we adhere to the "forall-or-nothing" rule more strictly. Related function: RnTypes.rnImplicitBndrs * The -Wimplicit-kind-vars warning has been deprecated. * Kind variables are no longer implicitly quantified in constructor declarations: data T a = T1 (S (a :: k) | forall (b::k). T2 (S b) -- no longer accepted data T (a :: k) = T1 (S (a :: k) | forall (b::k). T2 (S b) -- still accepted Related function: RnTypes.extractRdrKindSigVars * Implicitly quantified kind variables are no longer put in front of other variables: f :: Proxy (a :: k) -> Proxy (b :: j) f :: forall k j (a :: k) (b :: j). Proxy a -> Proxy b -- old order f :: forall k (a :: k) j (b :: j). Proxy a -> Proxy b -- new order This is a breaking change for users of TypeApplications. Note that we still respect the dpendency order: 'k' before 'a', 'j' before 'b'. See "Ordering of specified variables" in the User's Guide. Related function: RnTypes.rnImplicitBndrs * In type synonyms and type family equations, free variables on the RHS are no longer implicitly quantified unless used in an outermost kind annotation: type T = Just (Nothing :: Maybe a) -- no longer accepted type T = Just Nothing :: Maybe (Maybe a) -- still accepted The latter form is a workaround due to temporary lack of an explicit quantification method. Ideally, we would write something along these lines: type T @a = Just (Nothing :: Maybe a) Related function: RnTypes.extractHsTyRdrTyVarsKindVars * Named wildcards in kinds are fixed (Trac #16334): x :: (Int :: _t) -- this compiles, infers (_t ~ Type) Related function: RnTypes.partition_nwcs Implementation notes -------------------- * One of the key changes is the removal of FKTV in RnTypes: - data FreeKiTyVars = FKTV { fktv_kis :: [Located RdrName] - , fktv_tys :: [Located RdrName] } + type FreeKiTyVars = [Located RdrName] We used to keep track of type and kind variables separately, but now that they are on equal footing when it comes to scoping, we can put them in the same list. * extract_lty and family are no longer parametrized by TypeOrKind, as we now do not distinguish kind variables from type variables. * PatSynExPE and the related Note [Pattern synonym existentials do not scope] have been removed (Trac #16315). With no implicit kind quantification, we can no longer trigger the error. * reportFloatingKvs and the related Note [Free-floating kind vars] have been removed. With no implicit kind quantification, we can no longer trigger the error.
* base: Allow fusion for zip7 and relatedAlexandre2019-02-241-35/+75
| | | | | | | | | | | | | | | | | | Fixes #14037. Metric Decrease: T9872b T9872d Reviewers: bgamari, simonpj, hvr Reviewed By: simonpj Subscribers: AndreasK, simonpj, osa1, dfeuer, rwbarton, carter GHC Trac Issues: #14037 Differential Revision: https://phabricator.haskell.org/D5249
* Include closure header size in StgLamLift's estimationsSebastian Graf2019-02-231-4/+3
| | | | | | | | | | | While playing around with late lambda lifting, I realised that StgLamLift.Analysis doesn't consider the removed closure header in its allocation estimations. That's because contrary to what I thought, the total word count returned by `mkVirtHeapOffsets` doesn't include the size of the closure header. We just add the header size manually now.
* Fix regression incorrectly advertising TH supportHerbert Valerio Riedel2019-02-231-0/+8
| | | | | | | | `--supported-languages` must only advertise language extensions which are supported by the compiler in order for tooling such as Cabal relying on this signalling not to behave incorrectly. Fixes #16331
* Expression/command ambiguity resolutionVladislav Zavialov2019-02-238-344/+839
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch removes 'HsArrApp' and 'HsArrForm' from 'HsExpr' by introducing a new ambiguity resolution system in the parser. Problem: there are places in the grammar where we do not know whether we are parsing an expression or a command: proc x -> do { (stuff) -< x } -- 'stuff' is an expression proc x -> do { (stuff) } -- 'stuff' is a command Until we encounter arrow syntax (-<) we don't know whether to parse 'stuff' as an expression or a command. The old solution was to parse as HsExpr always, and rejig later: checkCommand :: LHsExpr GhcPs -> P (LHsCmd GhcPs) This meant polluting 'HsExpr' with command-related constructors. In other words, limitations of the parser were affecting the AST, and all other code (the renamer, the typechecker) had to deal with these extra constructors by panicking. We fix this abstraction leak by parsing into an intermediate representation, 'ExpCmd': data ExpCmdG b where ExpG :: ExpCmdG HsExpr CmdG :: ExpCmdG HsCmd type ExpCmd = forall b. ExpCmdG b -> PV (Located (b GhcPs)) checkExp :: ExpCmd -> PV (LHsExpr GhcPs) checkCmd :: ExpCmd -> PV (LHsCmd GhcPs) checkExp f = f ExpG -- interpret as an expression checkCmd f = f CmdG -- interpret as a command See Note [Ambiguous syntactic categories] for details. Now the intricacies of parsing have no effect on the hsSyn AST when it comes to the expression/command ambiguity. Future work: apply the same principles to the expression/pattern ambiguity.
* Add AnonArgFlag to FunTySimon Peyton Jones2019-02-2373-856/+1001
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The big payload of this patch is: Add an AnonArgFlag to the FunTy constructor of Type, so that (FunTy VisArg t1 t2) means (t1 -> t2) (FunTy InvisArg t1 t2) means (t1 => t2) The big payoff is that we have a simple, local test to make when decomposing a type, leading to many fewer calls to isPredTy. To me the code seems a lot tidier, and probably more efficient (isPredTy has to take the kind of the type). See Note [Function types] in TyCoRep. There are lots of consequences * I made FunTy into a record, so that it'll be easier when we add a linearity field, something that is coming down the road. * Lots of code gets touched in a routine way, simply because it pattern matches on FunTy. * I wanted to make a pattern synonym for (FunTy2 arg res), which picks out just the argument and result type from the record. But alas the pattern-match overlap checker has a heart attack, and either reports false positives, or takes too long. In the end I gave up on pattern synonyms. There's some commented-out code in TyCoRep that shows what I wanted to do. * Much more clarity about predicate types, constraint types and (in particular) equality constraints in kinds. See TyCoRep Note [Types for coercions, predicates, and evidence] and Note [Constraints in kinds]. This made me realise that we need an AnonArgFlag on AnonTCB in a TyConBinder, something that was really plain wrong before. See TyCon Note [AnonTCB InivsArg] * When building function types we must know whether we need VisArg (mkVisFunTy) or InvisArg (mkInvisFunTy). This turned out to be pretty easy in practice. * Pretty-printing of types, esp in IfaceType, gets tidier, because we were already recording the (->) vs (=>) distinction in an ad-hoc way. Death to IfaceFunTy. * mkLamType needs to keep track of whether it is building (t1 -> t2) or (t1 => t2). See Type Note [mkLamType: dictionary arguments] Other minor stuff * Some tidy-up in validity checking involving constraints; Trac #16263
* Remove bogus assertionSimon Peyton Jones2019-02-231-1/+3
| | | | | | | Remove a bogus assertion in FamInst.newFamInst (There is a comment to explain.) This fixes Trac #16112.
* Fix exprIsConApp_maybeSimon Peyton Jones2019-02-224-55/+74
| | | | | | | | | | | | | | | | | | | In this commit commit 7833cf407d1f608bebb1d38bb99d3035d8d735e6 Date: Thu Jan 24 17:58:50 2019 +0100 Look through newtype wrappers (Trac #16254) we made exprIsConApp_maybe quite a bit cleverer. But I had not paid enough attention to keeping exactly the correct substitution and in-scope set, which led to Trac #16348. There were several buglets (like applying the substitution twice in exprIsConApp_maybe, but the proximate source of the bug was that we were calling addNewInScopeIds, which deleted things from the substitution as well as adding them to the in-scope set. That's usually right, but not here! This was quite tricky to track down. But it is nicer now.
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